Touch function has become one of the essential features of many of today's electronic devices, and touch device is one of the common electronic devices capable of realizing the touch function. Basically, the present touch devices are categorized to: resistive type, capacitive type and optical type. Thus, various electronic devices can adopt various types of touch device based on different touch requirements.
FIG. 1 is a schematic structure view of a conventional optical touch device. As shown, the conventional optical touch device 100 includes a light guide set 110, a light emitting component 120 and a light sensing component 130. The light guide set 110 includes two light guide strips 112a, 112b and a strip mirror 114. The light guide strips 112a, 112b and the strip mirror 114 are arranged respectively along three of four sides of a rectangular trajectory; wherein the light guide strip 112a is configured to be opposite to the strip mirror 114, the light guide strips 112b is configured to be connected between the light guide strip 112a and the strip mirror 114, and the area within the rectangular trajectory is defined as a sensing area 116. In addition, the light emitting component 120 is disposed between the two adjacent ends of the light guide strips 112a, 112b and configured to provide lights to inside the light guide strips 112a, 112b. The light guide strips 112a, 112b each is configured to direct the lights from the light emitting component 120 to the sensing area 116. The light sensing component 130 is disposed near to one end of the light guide strip 112a and configured to have a field of view (FOV) of the entire sensing area 116.
The light sensing component 130 is configured to detect a light-blocking object in the sensing area 116 and determine the light-blocking object' position. As shown in FIG. 1, for example, a touch point (or, light-blocking object) A is located in the sensing area 116, and a corresponding mirroring point Al is formed on the strip mirror 114. Accordingly, a dark point A2, derived from the touch point A, and a dark point A3, derived from the mirroring point A1, are generated. Through detecting the two dark points A2, A3, the light sensing component 130 can obtain the distances d1, d2. And thus, the position (or, coordinate) of the touch point A can be obtained from the distances d1, d2, some known parameters such as the length of the X-axis of the sensing area 116, the width of the Y-axis of the sensing area 116, and some known conditions such as the shortest distance from the touch point A to the strip mirror 114 being equal to the shortest distance from the mirroring point A1 to the strip mirror 114. The means for the calculation of a coordinate are apparent to those ordinarily skilled in the art; no any unnecessary detail will be given here.
However, the conventional optical touch device 100 may have a blind zone 150 which is located near the lower left corner of the sensing are 116; wherein the blind zone means a specific area, in which the touch point's coordinate is difficult to be accurately calculated. For example, as shown in FIG. 1, a touch point B is located in the blind zone 150 of the sensing area 116 and a corresponding mirroring point B1 is formed on the strip mirror 114. Accordingly, the dark point B2, derived from the touch point B, and a dark point B3, derived from the mirroring point B1, may overlap; so, the coordinate of the touch point B is difficult to be calculated accurately.